A. Ultrasonication of Orange Juice Concentrate PA0 B. Homogenization of Juice Streams, Including Citrus Juice Streams
U.S. Pat. No. 3,352,693 to Berk, issued Nov. 14, 1967, discloses highly concentrated citrus juices (up to as high as 70.degree. Brix) which are alleged to be considerably less viscous than conventionally prepared juice concentrates. These less viscous, highly concentrated juice materials are obtained by subjecting the juice or concentrate to ultrasonic treatment. Example I discloses an orange juice concentrate (soluble solids content of 60.degree. Brix) which is subjected to ultrasonic waves having a frequency of 20,000 cycles per second. As shown in this Example, the longer the orange juice concentrate was subjected to ultrasonic treatment, the lower was its relative viscosity.
Berk, "Viscosity of Orange Juice Concentrates: Effect of Ultrasonic Treatment and Concentration," Food Technology, Vol. 18 (1964), pp. 1811-12, considers the scientific aspects of ultrasonic treatment of orange juice concentrates. FIG. 1 in this article shows a marked decrease in the relative viscosity of a 60.degree. Brix orange juice concentrate the longer it is subjected to ultrasonic treatment. FIG. 2 in this article compares pulp particles, before and after ultrasonic treatment. Based on this comparison, Berk observed that ultrasonic treatment caused a marked degree of disintegration of the membrane-like pulp particles and says that this effect may have contributed to the decrease in viscosity of the orange juice concentrate. Berk also notes that strong off-flavors (garlic, ozone-like, metallic) develop in the concentrate unless ultrasonic treatment is carried out under a vacuum or a nitrogen atmosphere.
Mizrahi and Berk, "Ultrasonic Waves in the Concentration of Citrus Juices," Process Biochemistry, Vol. 3, No. 10 (1968), pp. 25-27, also considers the scientific aspects of using ultrasonic waves in the concentration of citrus juices. Mizrahi et al say that the suspended particles and pectic substances present in citrus juice are the most important from the standpoint of the viscous structure of the juice. Based on experiments with 1% pectin solutions, they suggest that ultrasonic treatment depolymerizes the pectins present in the juice as the result of direct mechanical shear. They also say that ultrasonic treatment of citrus juice concentrates causes the disintegration of the suspended particles (citing the Berk article), but that the relationship between particle disintegration and viscosity "is not yet understood."
Lortkipanidze et al, "Use of a Homogenizer in a Citrus Juice Line," Konservnaya i Ovoshchesushil'naya Promyshlennost', No. 7 (1972), pp. 9-10, describes studies involving the incorporation of a homogenizer (OGB-type) into a juice production line. Before incorporation of the homogenizer, the system produced juice containing coarse pulp particles which had to be filtered off prior to bottling. The homogenizer (operated at a pressure of 30 MPa, i.e., about 4350 psi) was incorporated into the system between the vacuum unit for removal of excess essential oils and the vacuum apparatus where the juice was mixed with sugar syrup and deaerated. The juice obtained in the system having the homogenizer had finer sized pulp which did not require filtering prior to bottling.
Berishvili, "The Use of Ultrasound in the Production of Fruit Juices," Konservnaya i Ovoshchesushil'naya Promyshlennost', No. 10 (1976), pp. 19-20, describes the processing of fruit pulp with a rotary type ultrasonic homogenizer to provide completely homogenized single-strength fruit juice with pulp. After processing, the size of the juice particles is disclosed as not exceeding 50 microns (relative to a particle size of 250-300 microns for a control sample). Fruit juices derived from apple, peach, apricot, quince and mandarin fruit were processed in the homogenizer.